Apparatus for inspecting a moving web

Claim 1

APPARATUS FOR DETECTING IMPERFECTIONS IN A MOVING WEB COMPRISING A LIGHT SOURCE SPACED FROM A SIDE OF SAID WEB TO BE DETECTED AND ILLUMINATING A PORTION OF SAID WEB, PHOTOELECTRIC LIGHT SENSITIVE MEANS DISPOSED ADJACENT SAID WEB, A MULTI-FACED MIRROR DISPOSED ADJACENT TO SAID WEB AND MOUNTED FOR ROTATION ABOUT AN AXIS LYING IN A PLANE INTERSECTING AND EXTENDING SUBSTANTIALLY PARALLEL TO THE DIRECTION OF MOVEMENT OF SAID WEB, SHIELD MEANS SURROUNDING A MAJOR PORTION OF SAID MIRROR, SAID SHIELD MEANS BEING PROVIDED WITH A SCANNING WINDOW EMBRACING A DEFINED ANGLE FROM EDGE TO EDGE IN THE DIRECTION OF ROTATION OF SAID MIRROR, SAID MIRROR BEING POSITIONED SO AS TO SCAN SAID WEB FROM EDGE TO EDGE AT THE ILLUMINATED PORTION AND TO REFLECT THE LIGHT SO RECEIVED TO SAID LIGHT SENSITIVE MEANS, SIGNAL TRANSLATING MEANS CONNECTED TO THE OUTPUT OF SAID LIGHT SENSITIVE MEANS FOR TRANSLATING THE ELECTRICAL OUTPUT THEREOF INTO A SERIES OF PULSES INDICATING IMPERFECTIONS IN SAID WEB, AND INDICATING MEANS COUPLED TO SAID SIGNAL TRANSLTING MEANS AND RESPONSIVE TO THE SIGNAL RECEIVED UPON THE OCCURRENCE OF IMPERFECTIONS IN SAID WEB, SAID LIGHT SOURCE BEING DISPOSED ON THE OPPOSITE SIDE OF THE WEB FROM THAT BEING SCANNED AND BEING COMPRISED OF A SERIES OF IDENTICAL HIGH OUTPUT LAMPS ARRANGED IN LINEAR RELATIONSHIP TRANSVERSELY OF THE MOVING WEB AND VARYING IN DISTANCE FROM THE WEB IN NORMAL DIRECTION SUCH THAT THE OPTICAL DISTANCE FROM EACH LAMP VERTICALLY THROUGH SAID WEB AND TO ANY POINT ON SAID SCANNING MEANS IS APPROXIMATELY THE SAME REGARDLESS OF THE POINT ON THE WEB BEING SCANNED BY SAID ROTATING MIRROR.